Could busy, heterogeneous streets be better for the environment?

Our research combines field measurements in urban streets, Computational Fluid Dynamic (CFD) and laboratory modelling.

This creates a robust approach to researching problems in complex urban environments, where neither simplified experiments nor full CFD simulations can resolve the features of the airflow on their own.

Urban designers know that regular symmetrical street canyons, favoured as aesthetically pleasing in many European city centres, lead to accumulation of heat and pollutants. A vortex of recirculating air is created, which does not allow ventilation from the cleaner atmosphere above. Our research finds that even a little heterogeneity in a street layout, with some variety in rooftop heights along the length of the canyon, and small gaps along the length of the street, can improve the ventilation of the street and effectively prevent the recirculating vortex from occurring – resulting in streets that are better for the environment.

In urban environments, traffic-related pollution accumulates in streets and concentrations on the ground may exceed recommended levels for long periods of time. Understanding the detailed properties of the airflow patterns in every major city centre street is crucial if we are to reduce human exposure to pollution and dust, prevent particle settlement on historical building facades, and improve the transfer of heat out of the street into the atmosphere above the urban boundary layer.

A better understanding of these phenomena and the connection between airflow and the positioning of traffic lanes, green walls or trees, can help urban planners create better environments that are healthy, pleasant, and sustainable.